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Class definitions form the foundation for Java OOP. They are discussed in increasing detail in subsequent modules. This module sheds just a little more light on classes.

Revised: Mon Mar 28 00:23:43 CDT 2016

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Table of contents

Preface

This module is part of a collection of modules designed to help you learn to program computers.

This module sheds a little more light on the Java construct called a class .

Listings

  • Listing 1 . General syntax for defining a Java class.

Introduction

New types

Java makes extensive use of classes. When a class is defined in Java, a new type comes into being. The new type definition can then be used to instantiate (create instances of) one or more objects of that new type.

A blueprint

The class definition provides a blueprint that describes the data contained within, and the behavior of objects instantiated according to the new type.

The data

The data is contained in variables defined within the class (often called member variables, data members, attributes, fields, properties, etc. ).

The behavior

The behavior is controlled by methods defined within the class.

State and behavior

An object is said to have state and behavior . At any instant in time, the state of an object is determined by the values stored in its variables and its behavior is determined by its methods .

Class vs. instance

It is possible to define:

  • instance variables and instance methods
  • static or class variables and static or class methods.

Instance variables and instance methods can only be accessed through an object instantiated from the class. They belong to the individual objects, (which is why they are called instance variables and instance methods) .

Class variables and class methods can be accessed without first instantiating an object. They are shared among all of the objectsinstantiated from the class and are even accessible in the total absence of an object of the class.

The class name alone is sufficient for accessing class variables and class methods by joining the name of the class to the name of the variable or method using a period.

Defining a class in Java

The general syntax for defining a class in Java is shown in Listing 1 .

Listing 1 . General syntax for defining a Java class.
class MyClassName{ . . .} //End of class definition.

This syntax defines a class and creates a new type named MyClassName .

The definitions of variables, methods, constructors, and a variety of other members are inserted between the opening and closing curly brackets.

Miscellaneous

This section contains a variety of miscellaneous information.

Housekeeping material
  • Module name: Jb0170: Java OOP: A little more information about classes.
  • File: Jb0170.htm
  • Originally published: 1997
Disclaimers:

Financial : Although the Connexions site makes it possible for you to download a PDF file for thismodule at no charge, and also makes it possible for you to purchase a pre-printed version of the PDF file, you should beaware that some of the HTML elements in this module may not translate well into PDF.

I also want you to know that, I receive no financial compensation from the Connexions website even if you purchase the PDF version of the module.

In the past, unknown individuals have copied my modules from cnx.org, converted them to Kindle books, and placed them for sale on Amazon.com showing me as the author. Ineither receive compensation for those sales nor do I know who does receive compensation. If you purchase such a book, please beaware that it is a copy of a module that is freely available on cnx.org and that it was made and published withoutmy prior knowledge.

Affiliation : I am a professor of Computer Information Technology at Austin Community College in Austin, TX.

-end-

Questions & Answers

where we get a research paper on Nano chemistry....?
Maira Reply
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
Google
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
revolt
da
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
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Source:  OpenStax, Object-oriented programming (oop) with java. OpenStax CNX. Jun 29, 2016 Download for free at https://legacy.cnx.org/content/col11441/1.201
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